This invention relates to a system for air cooling integrated circuits and the like and, more particularly, the invention is concerned with providing a co-planar cooling system for cooling integrated circuits of the dual-in-line and flat pack variety wherein a sliding seal arrangement permits maximum opening size at inlet and outlet resulting in minimum pressure drop accomplished by providing a pressure seal across a slotted opening in a direction normal to the engagement.
The air cooling of integrated circuits of the dual-in-line and flat pack variety generally fall into two categories, in-line conduction and co-planar. The co-planar method of cooling is where the air passes as close as possible to the junction of the device resulting in the lowest operating temperature. It has been found that temperature improvements of 15.degree. to 20.degree. C. are obtainable by the co-planar approach versus the in-line conduction method. These comparisons are based on equal pressure drops and air flow rates.
Certain problems arise during the implementation of the co-planar method of cooling particularly as it relates to the inlet and exit sealing of the cooling air into a printed wiring assembly. The present technique shown in FIG. 1, utilizes a direct compression seal at the inlet and exit. Each opening is sized in one direction to be compatible with the 0.4 to 0.5 inch center to center printed wiring assembly spacing and in the other direction is limited by allowable printed wiring assembly board length within the total package. These type seals are commonly employed in the art and provide satisfactory sealing characteristics. However, from a pressure standpoint the configuration is limiting. The entering air, in traversing a path through the printed wiring assembly of FIG. 1 must twice change direction and, in addition, is forced to pass through two small openings at the entrance and exit which adds to the total pressure required to pass through the printed wiring assembly proper. These losses often account for 30 to 50 percent of the total through the unit from inlet to outlet and represents an intolerable penalty particularly where available pressure is at a premium.
In a typical electronic assembly cooling system, the total pressure available through the printed wire assembly is only 1.0 inch of water so that even a small allowance for air distribution losses places a severe penalty on heat transfer effectiveness for cooling. The hereinafter described invention overcomes the aforementioned difficulties by greatly reducing the losses due to inlet and exit conditions resulting in maximum available pressure for heat transfer to the integrated circuit packages.